[PATCH v2] usb: dwc3: gadget: Clear req->needs_extra_trb flag on cleanup

[Jack Pham]

OUT endpoint requests may somtimes have this flag set when
preparing to be submitted to HW indicating that there is an
additional TRB chained to the request for alignment purposes.
If that request is removed before the controller can execute the
transfer (e.g. ep_dequeue/ep_disable), the request will not go
through the dwc3_gadget_ep_cleanup_completed_request() handler
and will not have its needs_extra_trb flag cleared when
dwc3_gadget_giveback() is called.  This same request could be
later requeued for a new transfer that does not require an
extra TRB and if it is successfully completed, the cleanup
and TRB reclamation will incorrectly process the additional TRB
which belongs to the next request, and incorrectly advances the
TRB dequeue pointer, thereby messing up calculation of the next
requeust's actual/remaining count when it completes.

The right thing to do here is to ensure that the flag is cleared
before it is given back to the function driver.  A good place
to do that is in dwc3_gadget_del_and_unmap_request().

Fixes: c6267a51639b ("usb: dwc3: gadget: align transfers to wMaxPacketSize")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jack Pham <jackp@xxxxxxxxxxxxxx>
---
v2: Added Fixes tag and Cc: stable

Felipe, as I mentioned in the cover for v1, for stable (from 4.11 where
c6267a51639b first landed through 4.20), the fix needs to be modified to
assign to the separate req->unaligned and req->zero flags in lieu of
needs_extra_trb which appeared in 5.0-rc1 in:

	commit 1a22ec643580626f439c8583edafdcc73798f2fb
	Author: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>
	Date:   Wed Aug 1 13:15:05 2018 +0300

	    usb: dwc3: gadget: combine unaligned and zero flags

Do I need to send a separate patch for <= 4.20 or will you handle it?
It's straightforward really, the code change should instead be

+	req->unaligned = false;
+	req->zero = false;

Thanks,
Jack

 drivers/usb/dwc3/gadget.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 2ecde30ad0b7..e97b14f444c8 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -177,6 +177,7 @@ static void dwc3_gadget_del_and_unmap_request(struct dwc3_ep *dep,
 	req->started = false;
 	list_del(&req->list);
 	req->remaining = 0;
+	req->needs_extra_trb = false;
 
 	if (req->request.status == -EINPROGRESS)
 		req->request.status = status;
-- 
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